Ballast computer for underwater vehicles



BALLAST COMPUTER FOR UNDERWATER VEHICLES 3 Sheets-Sheet l Jan- 23, 1968 J. H. CHADWICK, JR., ETAL 3,364,738

BALLAST COMPUTER FOR UNDERWATER VEHICLES STERN PLANE ANGLE ADJUSTMENT Jain. 23, 1968 1 H. CHADWICK. JR., ETA. 3,364,733

BALLAST COMPUTER FOR UNDERWATER VEHICLES Filed Oct. 27, 1965 3 Sheets-Sheet L LD LO I I I I A I IN Ixo I I J I I I I I I D LLI LLI D.. (D

D LLI Il U) D I- I-J o O O .D -I .D o -O Q O 2 3 5 S2 3 Lo w zu In g+- Z JE L (29m L? rf) Ln qu) l0 q O I #D F D Q: l II 22 I\ q ac3 LL r Pq v I III I II II II II '4 INVENTORS JOSEPH H. CHADWICK VIRGEL E. WILLIAMS ATTY.

United States Patent filice 3,364,738 Patented Jan. 23, 1968 3,364,738 BALLAST COMPUTER FOR UNDERWATER VEHICLES Joseph H. Chadwick, Jr., Amityville, N.Y., and Virgel E.

Williams, Charlottesville, Va., assiguors, by mesne assignments, to the United States of America as represented bythe Secretary of the Navy Fiied Oct. 27, 1965, Ser. No. 505,436 3 Claims. (Cl. 73178) ABSTRACT F THE DISCLOSURE A ballast computer including a signal receiving demodulator which receives a signal from the control surfaces of the vehicle and passes the demodulated signal thru a lter to average out the short term variations in the signal. The signals are then displaced on meters. The position displayed by these meters are introduced into the potentiometer control elements of a computer which also receives signals corresponding to the speed of the vehicle and cornputes a value for the water to be added to or removed from the trim tanks of the vehicle to properly ballast the vehicle. The signals cor-responding to the positions of the control surfaces of the vehicle are phase compared in a transistorized phase comparator which makes up the demodulation.

The present invention relates to ballast computers and more particularly to ballast computers for use on underwater vehicles to achieve neutral trim and buoyancy by means of the vehicles ballast tanks.

When operating a vehicle, for example, a submarine below the surface, it is often desirable to maintain a constant depth. To accomplish this, the boats main ballast tanks are ooded to attain approximately neutral buoyancy. Then as the boat travels underwater several factors effect the precise positive or negative buoyancy. These include depth of operation, whether the boat is making water, changes in Water temperature, and most importantly for near surface control, the mean value of the suction force. The suction force has the effect of making the boat light overall and varies according to the state of the sea. On the larger atom-powered boats this effect may be as much as seven tons in a state tive head sea. At present, these various forces are compensated for essentially by trial and error. If the diving planes alone are used to compensate for all the normal out-of-buoyancy conditions, very little plane movement may be available to further compensate for buoyancy as these conditions vary. Thus, it is necessary to ood to or pump from one or more of the boats variable ballasting tanks to achieve a state of neutral trim. The amount of water to be pumped or ooded is presently determinable only approximately from the experience of the individual controlling such operations and consequently much time and variation in depth is consumed before satisfactory depth control is attained.

The present invention provides the means by which the correct amount of water to be pumped to, or flooded from, each of the variable ballast tanks can be determined. The corrections for proper ballasting are easily, swiftly, and accurately determined from the device of the present invention and the settings and readings can be properly taken and interpreted by inexperienced personnel.

The device of the present invention is also useful for initial trimming up just before the vehicle goes into a hovering or motionless state by eliminating out-of-buoyancy conditions that make achievement of the hovering state more time consuming.

An object of the present invention is, therefore, to provide a means for determining proper ballasting in underwater vehicles.

A further object is to provide a means for determining ballasting which may be operated by inexperienced personnel.

Another object is to provide a ballast computer which combines indicated and known values to produce an indication of the quantity of water necessary to achieve neutral trim.

Another object is to provide a ballast computer which combines indicated and known vaiue to produce an indication of the quantity of water necessary to achieve neutral trim when the vehicle is operating near the surface.

A nal object is to provide a ballast computer to facilitate the elimination of out of trim conditions before the attempted achievement of the hovering state.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein a preferred embodiment is disclosed. 1t should be noted that the device will be described with reference to its use with a submarine. The device, however, is adaptable for use in any underwater vehicle that uses the expedient of variable ballasting to maintain neutral buoyancy.

FIG. l is a block flow diagram of the preferred embodiment of the invention;

FIG. 2 is a schematic diagram of one of the demodulaters indicated in FIG. 1; and

FIG. 3 is a schematic diagram of the computer indicated in FIG. 1.

The general operation of the preferred embodiment can be described with reference to FIG. 1. The computer system indicated generally by reference numeral 1G is designed to solve the steady state equations of motion calculated for the submarine on which the device is installed. The actual equations solved by the computer are where:

T :the pounds of water to be transferred from after to forward trim, or vice versa,

F :the pounds of water to pump or flood from the auxiliary tanks,

U2=the square of the submarine speed,

6=the pitch angle relative to the horizontal,

S5=the stern plane diving angle,

S6=the sailplane angle (fairwater plane),

The constant K1 through K6 are a function of the known physical parameters of the submarine; e.g. (1) the coefficients of longitudinal equations of motion, (2) the length of the submarine, (3) the distance of the auxiliary tank from the center of buoyancy, and (4) the distance between trim tanks.

Thus, the computer requires for inputs parameters representing the angles of the two sets of planes (sai'lplane and sternplane) which are necessary to maintain constant depth, the angle of the boat with respect to the horizontal, and the speed of the boat. From these parameters the computer determines (l) the water to be pumped or ooded to the auxiliary tank to achieve neutral buoyancy and (2) the water to be transferred between the forward and aft trim tanks to achieve neutral trim.

When water corresponding to the above values has been pumped from or flooded to the respective tanks, the submarine will remain at constant depth Without constant plane deection.

The angle indications are derived by the three demodulating systems shown by reference numerals 12, 14 and 16 in FIG. 1. An exemplary one of the demodulating systems, specifically the circuit for the stern plane signal, is shown in FIG. 2. The circuits for the other two angle inputs are substantially identical so description of this single circuit should be suiiicient as a description for all three.

The signa-l appearing across terminals 18 and 20 is taken from the main stern plane synchro transmitting unit which is activated by movements through positive and negative angular displacements of the stern planes. Thus, the phase angle of the signal input varies with respect to the phase angle of the reference voltage appearing across terminals 22 and 24. The reference voltage is increased by transformer 26 and applied across the baseemitter circuits of paired transistors 28 and 30. The same reference voltage but of opposite phase is applied to the base-emitter circuit of the other pair of transistors 32 and 34.

The signal voltage is transformed at 36, and applied to the collector of transistor 28 in phase, and to transistor 32 180 out of phase. Thus, a signal input in phase with the reference voltage would produce a positive DC ripple at terminal 38, a signal 90 out of phase would produce no DC output, and a signal 180 out of phase would produce a negative DC ripple. The DC signal is then filtered through resistors 48, 42, and 44, and the capacitor network indicated generally at 46. The filter 48 has along time constant, on the order of 60 seconds, so that the output seen by meter 50 represents an average value. This is done because in actual operation the planes may be varying frequently to compensate for short duration changes and what is needed for ballast computation is the mean value, representing in this case, the constant defiection of the stern planes necessary to maintain depth. For this reason, readings are not taken `for approximately two minutes after any major change in depth so that the indication has a chance to settle down and represent a true mean value. As was previously noted, the sail plane and trim demodulators are substantially identical except that they receive signals from the sail plane servo and horizontal ygyro or other horizontal reference, respectively. Their outputs are indicated on meters 52 and 54.

The computer section is comprised of analog units which have the aforementioned steady-state equations and the trim and auxiliary tank locations of the particular boat built into them. That is, the constant coefiicients of the foregoing equations represent the fixed factors relating to the problem, such as: The length of the vehicle, the xed distance of the tanks relative to the center of gravity and the distances between trim tanks. Because these factors are constants they can be introduced schematically into the computer by the bias set into the potentiometers 56, 58 and 60 and by the use of fixed resistors 56a, 56b, 58a, 58h, 60a, 60b, 60C and 71. Each of the set of resistors indicated as (D, etc. is adjusted for both network 68 and 70 to represent the speed coefficient for a particular speed of the craft. Each of these correspondingly numbered sets is designed to be simultaneously switched into its respective net work to introduce the speed factor into the solution of the equation. The potentiometers 56, 58 and 60 are adjused in accordance with the indication of meters 50, 52 and 54 respectively. The computer has three input potentiometers 56, 58 and 60 that are adjusted to apply the trim angle input and the two plane angle inputs to networks 68 and 70 of precision resistors which divide the signal according to the position of the speed selector switch 62. Thus, the computer sums the inputs for trim and plane angles and each of two networks 68 and 70 divides them according to the set speed and displays the results on meters 64 and 66 for the trim tanks and auxiliary tanks, respectively. The readings of these meters provide the information for adjusting the ballast in the respective tanks.

The trim tank meter is calibrated in pounds of water to be transferred forward or aft to effect neutral trim and the auxiliary tank meter is calibrated in pounds of water to be pumped from or flooded to the auxiliary tanks to effect neutral buoyancy.

The final step in the operation is to pump or flood water to the various tanks according to the indications on the two meters.

In summary, what has been provided by the instant invention is a simple, accurate, and easy to operate, ballast computer which speedily will determine the correct amount of ballast to be transferred, pumped, or flooded so as to keep the submarine at a constant depth without dependence on large deflections of the boats planes.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For example the device may be used in a simplified form to compute only out of trim conditions by taking a signal from the horizontal control surfaces and displaying it only after neutral buoyancy has been determined by other methods. Then the signal would be combined with a signal set in the computer from the speed of the boat and would indicate from the `computer output the amount of water to be pumped between the trim tanks to achieve neutral trim.

What is claimed is:

1. A system for determining the ballasting of an underwater vehicle having balla-st tanks and a servo-motor system for controlling the position of its control surfaces comprising:

means responsive to the positions of the servo-motor control system for producing a first plurality of A.C. electrical input signal corresponding to the angular position of the control surfaces of the vehicle; demodulator means for each of said position signals; lter means for determining the average value of said demodulated position signals;

means to display said average position signals;

means for producing a second plurality of signals proportional to said displayed signals;

means for generating a signal proportional to the speed of said vehicle;

means for combining said second plurality of signals and said speed signal; and

means responsive to said combined signals for computing water levels required in the ballast tanks to ballast the vehicle.

2. Apparatus according to claim 1 wherein said demodulating means includes a phase-sensitive demodulator controlled by a reference voltage.

3. Apparatus according to claim 1 wherein said control means are rheostats.

References Cited UNITED STATES PATENTS DAVID SCHONBERG, Primary Examiner.

LOUIS R. PRINCE, Examiner.

N. B. SIEGEL, Assistant Examiner. 

